The machining of workpieces is often very complex, and can comprise a plurality of chip-generating and non-chip-generating operations on different processing machines in order to produce the finished component from a blank. In all production sequences, it is essential in this context that the workpiece assume a defined position on the respective machine tool for each operation.
For this purpose, it is usual in practice first to clamp the unmachined workpiece onto a carrier pallet, and then to clamp the entire unit onto the respective machine tool, by way of multiple draw-in bolts that are provided on the back side of the carrier pallet and are configured as centering elements, by the fact that the draw-in bolts are inserted into corresponding quick clamping units that are provided on the machine table. In production, it is possible in this manner to regard the positions of the quick clamping devices as a fixed machine parameter, so that it is necessary in each case only to position the workpiece precisely on the carrier pallet. The actual clamping and reclamping of the unit comprising the workpiece and carrier pallet onto machines can then be accomplished very quickly and easily, with no need for further positioning.
The known mechanical/hydraulic clamping devices on which the present invention is based are configured either as so-called build-up cylinders--which form closed units and can be clamped onto a machine table, a baseplate, or the like--or as so-called built-in cylinders--which can be recessed into the machine tables, quick-release plates, dies, etc. The known built-in cylinders are inserted directly into a recess of the machine table or into a corresponding base element; a pressure space is then formed between the built-in cylinder and the recess of the machine table, and can be acted upon by a hydraulic medium in order to release the clamping device.
The use of such built-in cylinders often proves problematic because the machine tables often do not possess the necessary casting quality, so that the receptacles cannot be manufactured with the necessary accuracy and sealing problems thus occur. In addition, the formation of cavities can in some cases greatly degrade the service life of the pistons of the clamping devices or that of the seals. In addition, the clamping forces are directed into the machine table, base element, or the like, so that distortion can occur therein.